Synthesis of a Heterometallic Trinuclear Cluster Containing Ruthenium and Cobalt and Its Reactivity with Internal Alkynes

A heterometallic tetrahydrido cluster composed by ruthenium and cobalt, (Cp*Ru)₂(Cp*Co)­(μ-H)₃(μ₃-H) (<b>1</b>) (Cp* = η⁵-C₅Me₅), was exclusively synthesized by the reaction of Cp*Ru­(μ-H)₄RuCp* with (Cp*CoCl)₂ in the presence of LiBEt₃H. X-ray diffraction and VT-NMR studies showed that <b>1</b> has a similar structure to the Ir and Rh analogues in terms of the positions of the hydrido ligands, but the size of the trinuclear site is considerably smaller than that of the iridium analogue because of the smaller covalent radius of cobalt. Like the iridium analogue, complex <b>1</b> reacted with internal alkynes to yield an equilibrated mixture of perpendicularly coordinated alkyne complexes. However, the structure of the major isomer was different from that of the iridium analogue: the alkyne ligand on the Ru₂Co core was preferentially coordinated to one of the Ru–Co bonds